1. Field of the Invention
The present invention relates to a flexible diaphragm valve device and more particularly to valve devices of the type which are employed in metering units which are adapted to be used with intravenous (I.V.) delivery sets.
2. Description of the Prior Art
Heretofore, flexible diaphragm valve devices for metering units were known. In our U.S. Pat. No. 4,121,584 filed Oct. 15, 1976, we described an I.V. metering unit having a flexible diaphragm valve device which employed a polyurethane diaphragm. The diaphragm of this metering unit was permanently formed over the valve seat area and over the metering chamber area by heat forming. The preformed areas were difficult to align precisely with the recessed areas in the valve case. When the preformed portions of the diaphragm do not exactly align and fit the corresponding recessed areas in the valve case, the diaphragm was found to be prone to early failure.
Planar or flat sheet diaphragms have been used in valve devices in cooperation with recessed valve seats. It is known that flat diaphragms cooperating with recessed valve seats are operable. However, valves of such construction tend to be subject to early failure due to the characteristic tendency of rubber to rupture easily when it is under tension and subject to frictional scrubbing as occurs with diaphragms cooperating with recessed valve seats. Attempts to remedy this shortcoming have proven costly and have introduced new problems such as increasing the energy required for valve actuation.
It would be desirable to eliminate the problems of the prior art flexible diaphragm valve devices in a simpler and cheaper structure while retaining the ease of actuation and durability of the valve described in our U.S. Pat. No. 4,121,584.